I understand that there are two ways to measure rpm's with elite drivo:

A - There is an integrated measure of rpm I don't have do to anything and its working just out of the boxB - I can use the external cadence sensor that was inside the elite drivo box

Question: because I want to use the pedal stroke analysis tool it is recommended to use the external cadence sensor for better accuracy (B). But how can I check that the external sensor is now actually working correctly and that not the sensor from (A) is still in use?